1. Technical Field
The present invention is generally related to damper mechanisms and, more particularly, to an electrorheological magnetic (ERM) fluid-based damper for controlling the deployment and operation of spacecraft appendages such as solar array panels, antennas, optical platforms, and other spacecraft structural elements.
2. Discussion
Deployment of spacecraft appendages such as antenna dishes, solar panel arrays, etc. are mission-critical operations that must be accomplished reliably and in a controlled fashion without causing damage or excessive disturbances and oscillations in the spacecraft. Conventional spacecraft typically use magnetic-type devices for deployment mechanisms. These devices include controllable electric motors and damper devices known as "eddy current" dampers.
In light of recent deployment problems, civilian and defense spacecraft customers are requiring torque margins for deployment mechanisms many times greater than earlier levels. This torque margin, as well as the revised requirements for damping rate, response time, and control, are beyond the capabilities of the typical presently used damper and control devices. Thus, the enhanced requirements have created a need for more powerful deployment mechanisms with much greater damper and control system performance.
It has now been found desirable to utilize electrorheological magnetic (ERM) fluid for enhanced damping control. ERM fluids undergo a change in apparent viscosity when subjected to a magnetic field. In the presence of a magnetic field, the particles become polarized and are thereby organized into chains and columns of particles within the fluid. The chains and columnar arrangement of particles act to increase the apparent viscosity or flow resistance of the overall material. In the absence of a magnetic field, the particles return to an unorganized or free state and the apparent viscosity or flow resistance of the overall material is correspondingly reduced.
Due to its variable resistance, ERM materials have been found useful in providing varying damping forces as well as in controlling torque and/or pressure levels. ERM fluids exhibit high yield strengths and are capable of generating great damping forces. Furthermore, ERM materials are activated by magnetic fields which are easily produced by simple, low-voltage electromagnetic coils.
Accordingly, it would be desirable to provide a deployment mechanism employing an ERM fluid based damper capable of meeting advanced spacecraft requirements. The ERM damper could be used to control the driving force or torque of a reliable spring or motor-driven actuator. Furthermore, it would be desirable to provide an ERM damper capable of fixed or variable damping control or a combination thereof.